U.S. patent number 10,213,242 [Application Number 14/376,520] was granted by the patent office on 2019-02-26 for fastening device and tool for surgical holding systems.
This patent grant is currently assigned to CREAHOLIC S.A.. The grantee listed for this patent is Creaholic S.A.. Invention is credited to Markus A. Muller, Vincent Vaucher.
United States Patent |
10,213,242 |
Vaucher , et al. |
February 26, 2019 |
Fastening device and tool for surgical holding systems
Abstract
A fastening device for surgical holding systems includes a
holding element and a fastening element with a ball joint, which
can be locked by way of rotating an eccentric ring in the holding
element. The joint socket defines a joint inner surface of the ball
joint and the joint head a joint outer surface of the ball joint.
When the eccentric ring clamps the joint head with respect to the
joint socket, the position of three contact locations of the ball
joint which lock the ball joint are unambiguously defined due to
the shape of at least one of the three elements: joint socket,
joint head and eccentric ring.
Inventors: |
Vaucher; Vincent (Eschert,
CH), Muller; Markus A. (Zurich, CH) |
Applicant: |
Name |
City |
State |
Country |
Type |
Creaholic S.A. |
Biel |
N/A |
CH |
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Assignee: |
CREAHOLIC S.A. (Biel,
CH)
|
Family
ID: |
47709745 |
Appl.
No.: |
14/376,520 |
Filed: |
February 5, 2013 |
PCT
Filed: |
February 05, 2013 |
PCT No.: |
PCT/CH2013/000022 |
371(c)(1),(2),(4) Date: |
October 06, 2014 |
PCT
Pub. No.: |
WO2013/116952 |
PCT
Pub. Date: |
August 15, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20150045840 A1 |
Feb 12, 2015 |
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Foreign Application Priority Data
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Feb 6, 2012 [EP] |
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12405017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
17/8038 (20130101); A61B 17/8047 (20130101); A61B
17/8894 (20130101); A61B 17/8042 (20130101); A61B
17/8605 (20130101); A61B 17/8875 (20130101); A61B
17/1728 (20130101); A61B 17/8695 (20130101); A61B
17/8685 (20130101); A61B 2090/031 (20160201); A61B
2017/00004 (20130101) |
Current International
Class: |
A61B
17/80 (20060101); A61B 17/17 (20060101); A61B
17/88 (20060101); A61B 17/86 (20060101); A61B
17/00 (20060101); A61B 90/00 (20160101) |
Field of
Search: |
;606/286-290 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1346697 |
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Sep 2003 |
|
EP |
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20091017656 |
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Feb 2009 |
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WO |
|
Primary Examiner: Lawson; Matthew
Attorney, Agent or Firm: Rankin, Hill & Clark LLP
Claims
The invention claimed is:
1. A fastening device for surgical holding systems, comprising a
holding element and a fastening element that are mechanically
connectable to one another, and a clamping element, wherein the
holding element comprises a joint socket, and the fastening element
comprises a joint head, wherein the joint socket and the joint head
are shaped in a manner corresponding to one another and form a ball
joint, and movement of the ball joint is lockable by way of the
clamping element, wherein the clamping element is an eccentric ring
that, on rotation, clamps the joint head with respect to the joint
socket, wherein the joint socket defines a joint inner surface of
the ball joint, and the joint head defines a joint outer surface of
the ball joint, the joint outer surface being part of a sphere,
wherein the ball joint is formed by contact between the joint inner
surface and the joint outer surface, wherein the eccentric ring is
rotatably arranged on the holding element and on rotation of the
eccentric ring with respect to the holding element, the eccentric
ring is pressed against the joint outer surface of the ball joint
to lock the movement of the ball joint.
2. The fastening device according to claim 1, wherein the ball
joint can be locked independently of the position of the fastening
element in the holding element.
3. The fastening device according to claim 1, wherein either the
joint inner surface comprises exactly two or exactly three inwardly
projecting contact regions, or the joint outer surface of the ball
joint comprises exactly two or exactly three outwardly projecting
contact regions, and thereby, when the eccentric ring clamps the
joint head with respect to the joint socket but no deformation has
taken place on these parts, exactly three or four contact locations
are present between the joint inner surface and the joint outer
surface of the ball joint.
4. The fastening device according to claim 1, wherein the joint
inner surface comprises exactly two or exactly three inwardly
projecting contact regions and the joint outer surface of the ball
joint comprises no outwardly projecting contact regions.
5. The fastening device according to claim 1, wherein the eccentric
ring comprises two projecting contact regions.
6. The fastening device according to claim 5, wherein connection
lines of the two contact regions form an angle of less than
170.degree., in particular an angle of less than 100.degree. to a
middle axis of the eccentric ring.
7. The fastening device according to claim 1, wherein two of the
three contact locations on two contact regions arise by a
deformation of the eccentric ring at two sides of a flexurally weak
location which runs along the periphery of the eccentric ring.
8. The fastening device according to claim 7, wherein the
flexurally weak location lies opposite to gap in the ring, the gap
defining two ends that are spaced apart by the gap.
9. The fastening device according to claim 1, wherein: the holding
element includes a lead-through for the fastening element; the
joint inner surface comprises three projections that project
inwardly from a periphery of the lead-through, are arranged on a
side of the holding element that lies opposite the eccentric ring,
and are arranged essentially uniformly on the periphery of the
lead-through.
10. The fastening device according to claim 1, wherein the joint
head comprises exactly two or exactly three projections that
project outwardly from the joint head and define the joint outer
surface of the ball joint; and wherein the joint inner surface has
no inwardly projecting contact regions.
11. The fastening device according to claim 1, wherein the
eccentric ring is rotatably arranged on the fastening element, and
the joint head comprises an intermediate element that can be
pressed against the joint socket of the holding element by way of
rotating the eccentric ring and by way of this forms a first
contact location and locks the ball joint, and the joint head
comprises at least two segments that are arranged lying opposite
the intermediate element with respect to the joint head, wherein
each of the at least two segments defines a contact region and,
with this, a further contact location of the ball joint.
12. The fastening device according to claim 1, wherein the
eccentric ring is rotatably arranged on the fastening element, and
a section of the eccentric ring can be pressed against the joint
socket of the holding element by way of rotating the eccentric ring
and by way of this forms a first contact location and locks the
ball joint, and the joint head comprises at least two segments that
are arranged lying opposite the first contact location with respect
to the joint head, wherein each of the at least two segments
defines a contact region and, with this, a further contact location
of the ball joint.
13. The fastening device according to claim 1, wherein the
fastening element is designed essentially rotationally
symmetrically with respect to a longitudinal axis of the fastening
element, and a plane that leads through the three contact locations
does not contain this longitudinal axis.
14. The fastening device according to claim 1, wherein the
eccentric ring lies in a ring plane, and a plane which leads
through the three contact locations, has an angle of maximal 45
degrees to the ring plane.
15. The fastening device according to claim 1, wherein a smallest
distance between the three contact locations is at least 0.8 times
the diameter of the joint head.
16. The fastening device according to claim 1, comprising a lock-in
element for a locking-in fixing of the eccentric ring with regard
to a rotation with respect to the holding element.
17. The fastening device according to claim 1, wherein the
eccentric ring comprises at least one undercut opening for
introducing a tool for rotating the eccentric ring, wherein a first
region of the opening through which the tool is inserted is smaller
than a second region of the opening engaged by the tool for
rotating the eccentric rind.
18. The fastening device according to claim 1, wherein when the
eccentric ring clamps the joint head with respect to the joint
socket, positions of three contact locations of the ball joint that
lock the ball joint are defined by a shape of at least one of the
joint socket, the joint head and the eccentric ring, and the three
contact locations are present between the joint outer surface of
the ball joint and the joint socket or the eccentric ring.
19. A fastening device for surgical holding systems, comprising a
holding element and a fastening element that are mechanically
connectable to one another, and a clamping element, wherein the
holding element comprises a joint socket, and the fastening element
comprises a joint head, wherein the joint socket and the joint head
are shaped in a manner corresponding to one another and form a ball
joint, and the movement of the ball joint is lockable by way of the
clamping element, wherein the clamping element is an eccentric ring
that, on rotation, clamps the joint head with respect to the joint
socket, wherein the joint socket defines a joint inner surface of
the ball joint, and the joint head defines a joint outer surface of
the ball joint, the joint outer surface being part of a sphere,
wherein the ball joint is formed by the joint inner surface of the
ball joint and the joint outer surface of the ball joint, wherein
the joint head includes a receiver for engaging a tool used to
rotate the fastening element, wherein when the eccentric ring
clamps the joint head with respect to the joint socket, the
receiver is not covered by the eccentric ring such that the
receiver is accessible for engaging the tool.
20. A fastening device for surgical holding systems, comprising a
holding element and a fastening element that are mechanically
connectable to one another, and a clamping element, wherein the
holding element comprises a joint socket, and the fastening element
comprises a joint head, wherein the joint socket and the joint head
are shaped in a manner corresponding to one another and form a ball
joint, and the movement of the ball joint is lockable by way of the
clamping element, wherein the clamping element is an eccentric ring
that, on rotation, clamps the joint head with respect to the joint
socket, wherein the joint socket defines a joint inner surface of
the ball joint, and the joint head defines a joint outer surface of
the ball joint, the joint outer surface being part of a sphere,
wherein the ball joint is formed by the joint inner surface of the
ball joint and the joint outer surface of the ball joint, wherein
the ball joint can be locked independently of the position of the
fastening element in the holding element.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to the field of surgical holding systems and
in particular to a fastening device for surgical holding systems,
to a surgical holding element and to a tool for surgical holding
systems.
Description of Related Art
Surgical holding systems, for example for fixing broken bones,
often consist of plates that are fastened into the bone by way of
screws. The plates comprise openings, into which the screws are
inserted at different angles. A surgical holding system is known
from WO 2010/121388 A1, which is owned by the present applicant,
with which a joint head of a screw with a joint socket in a plate
forms a ball joint. The orientation of the screw in the joint
socket is fixable by way of an eccentrically designed clamping
ring. The clamping ring for this is rotatably mounted in the plate
and on rotation clamps against the joint head of the screw.
Thereby, the problem of exactly two contact points between the
joint head on the one hand and the joint socket and the clamping
ring on the other hand results with the clamping, due to the
geometry of the ball joint and the clamping ring. This is a
consequence of the non-ideal shape of these parts due to
manufacturing tolerances. Although it is then possible for the
parts to plastically deform by way of continued, heavy tensing of
the clamping ring, and for further contact points to arise,
however, if this does not happen then the two contact points define
an axis, about which the joint head can rotate with respect to the
joint socket, so that the connection is not correctly locked
(arrested) under all circumstances.
SUMMARY OF THE INVENTION
It is therefore the object of the invention, to provide a fastening
device for surgical holding systems, and a surgical holding
instrument of the initially mentioned type, which overcome the
disadvantages mentioned above.
A further object of the invention to create a tool, with which the
fastening device can be locked or released in a secure and simple
manner, and also the screw can be screwed in or screwed out.
In accordance with the present invention, the fastening device,
provided for surgical holding systems, includes at least one
holding element and a fastening element that can be mechanically
connected to one another. The holding element includes a joint
socket, and the fastening element includes a joint head. The joint
socket and the joint head preferably, at least in sections, with
regard to their shape correspond to one another and together form a
ball joint. The movement of the ball joint can be locked via a
clamping element. The clamping element of the fastening device
includes a ring with an eccentric shape, which on rotation of the
ring clamps and/or tenses the joint head with respect the joint
socket. The joint socket and a ring inner surface of the eccentric
ring together define a joint inner surface of a joint shell
(socket), in which the joint head is mounted, wherein an outer ball
surface of the joint head lies opposite the joint inner surface.
Thereby, when the eccentric ring clamps the joint head with respect
to the joint socket, the position of three contact locations of the
ball joint, which lock the ball joint, is unambiguously defined due
to the shape of at least one of the three elements--the joint
socket, the joint head and the eccentric ring.
It is noted that the inventive arrangement is in sharp contrast to
connection systems wherein, for example, a smooth surface or one
which is grooved, profiled or structured in another manner is
present on the joint inner surface and/or the ball surface. Such
surfaces lead to a multitude of contact locations whose position,
however, is subject to chance and thus not unambiguously defined.
With the fastening device according to the present invention, in
contrast, there are at least three contact locations, but this does
not exclude yet a fourth unambiguously defined contact location
being present under certain geometric conditions, without a
deformation on these parts having taken place. Moreover, it also
does not exclude further contact locations arising with an
increasing clamping, whose position however is not defined.
On account of this, it is possible to screw the screws into the
bone at a relatively freely selectable angle, and, independently of
the exact position of the screws, to lock these with the plate in
an angularly stable manner thanks to the three-point connection
between the joint socket (with clamping element) and the joint
head.
The eccentric ring--irrespective of whether it is rotatably
arranged on the holding element or on the fastening element--as a
rule on the one hand itself is eccentrically mounted with respect
to the center of the ball joint, thus rotatable about an axis which
does not lead through this center. On the other hand, an inner
surface of the ring which essentially follows a cylindrical shape
and which, at least in sections or in a pointwise manner, is in
contact with the fastening element, and outer surface of the ring
which follows an essentially cylindrical shape and which at least
in sections or in a pointwise meaner is in contact with the holding
element, are not concentric to one another.
According to one variant of the fastening device, envisaged for
surgical holding systems, it comprises at least one holding element
and a fastening element, which can be mechanically connected to one
another. The holding element includes a joint socket, and the
fastening element a joint head. The joint socket and the joint head
preferably, at least in sections, correspond to one another in
their shape, and together form a ball joint. The movement of the
ball joint is lockable by way of a clamping element. The clamping
element of the fastening device comprises a ring with an eccentric
shape, which on rotation of the ring clamps and/or tenses the joint
head with respect to the joint socket. The joint socket and a ring
inner surface of the eccentric ring together define a joint inner
surface of a joint shell (socket), in which the joint head is
mounted, wherein an outer ball surface of the joint head lies
opposite the joint inner surface. Thereby: either the joint inner
surface comprises exactly two or exactly three inwardly projecting
contact regions, or the joint outer surface comprises exactly two
or exactly three outwardly projecting contact regions, wherein when
the eccentric ring clamps the joint head with respect to the joint
socket, but no deformation on these parts has taken place, exactly
three contact locations or also exactly four contact locations are
present between the joint inner surface and the joint outer
surface.
With regard to terminology, it is to be noted that as a rule the
term "contact region" (mostly as a projecting contact region)
stands for a design of the element that is given by the shape of an
element--thus the joint socket, joint head or clamping element--
and, thus, which is also recognisable on the element itself. The
term "contact location" in contrast indicates points or regions in
which the elements lie on one another and the greatest forces are
transmitted or occur when clamping. As to where exactly the contact
locations occur is dependent on the mutual arrangement of the
elements and on the position of their contact regions. Some of the
contact regions become contact locations. Conversely, some contact
locations result at contact regions, and other contact locations
typically result by way of one or in particular two contact regions
pressing onto the elements from an opposite side of the joint.
In one embodiment, the eccentric ring is rotatably arranged on the
holding element and on rotation of the eccentric ring with respect
to the holding element, the eccentric ring itself or an
intermediate element moved by the eccentric ring is pressed against
the joint outer surface, or against the joint head.
An outer surface of the ring, along which the ring is rotatable in
the holding element, has a rotationally symmetrical shape. The ring
inner surface forms a contact surface with the joint head and at
least approximately can form a section of a ball surface. On
rotating the clamping element, the contact surface presses against
the ball-section-shaped outer surface of the joint head.
Thus, in the region of the ring inner surface and of the joint
socket with regard to the joint head two or three contact regions
that project inwards with respect to the remaining points of this
region are present, and/or two or three contact regions that
project outwards with respect to the remaining points of the ball
surface are present on the ball surface.
In one embodiment, the eccentric ring is rotatably arranged on the
fastening element and on rotation of the eccentric ring with
respect to the fastening element, the eccentric ring itself or an
intermediate element moved by the eccentric ring is pushed against
the joint inner surface, or against the joint socket.
According to different embodiments, for example, two of the defined
contact locations arise at two corresponding contact regions by way
of deformation of the eccentric ring, in particular on two sides or
ends (considered along the periphery) of a flexurally weak location
running along the periphery of the eccentric ring. The embodiments
described with regard to the invention at other places and with
projecting contact regions on the eccentric ring can basically also
be realised with this variant with a deformation of the eccentric
ring.
According to different embodiments, the joint inner surface has
exactly two or exactly three inwardly projecting contact regions,
and the ball surface no outwardly projecting contact regions. These
contact regions of the joint inner surface can be formed on the
ring and/or on the joint socket, wherein the total number of the
projecting contact regions should be smaller or equal to three or
four or five.
It is generally advantageous if the defined contact locations which
can be formed according to the different embodiments, considered in
a projection in a plane, in which the holding element extends, are
distributed at least approximately uniformly on the joint surfaces
of the ball joint.
Generally, for example, the following combinations of contact
regions and contact locations resulting therefrom are possible: 1.
Three projecting contact regions on the ring, no projecting contact
region on the joint socket. On clamping, depending on inaccuracies
due to tolerance, a contact location of the joint socket will
absorb the clamping force that is introduced through the three
projecting contact regions on the ring into the joint head. A
situation then sets in between this contact location and the two
contact regions of the ring that lie opposite this contact
location, as also results in the following combination, i.e. on
clamping the result is that two contact locations are present on
the ring and one contact location on the joint socket. 2. Two
projecting contact regions on the ring, no projecting contact
region on the joint socket. The two contact regions on the ring, on
clamping, press the joint head against a contact location that, on
the bisector of the connection lines of the two contact regions to
the center of the joint head, lies opposite the two contact
regions. The location of this contact location, thus when the ring
is in the clamping position, is defined by the position of the two
contact regions and with the two contact regions forms the
three-point connection between the joint socket/ring and joint
head. The result is therefore that two contact locations are
present on the ring and one contact location on the joint socket.
3. Two projecting contact regions on the ring, one projecting
contact region on the joint socket. The latter is to be arranged at
a location where the contact location described above lies. The
result therefore is that here too, two contact locations are
present on the ring and one contact location on the joint socket.
4. One projecting contact region on the ring, two projecting
contact regions on the joint socket. Analogously to the third
combination, the one contact location is to be arranged on the ring
where the bisector of the connection lines of the two contact
regions of the joint socket to the center of the joint head passes
through the ring inner surface at the opposite side. The result is,
therefore, two contact locations on the joint socket and one
contact location on the ring. 5. No projecting contact region on
the ring, two projecting contact regions on the joint socket.
Analogously to the second combination, the one contact region on
the ring lies where the bisector of the connection lines of the two
contact regions of the joint socket to the center of the joint head
passes through the ring inner surface at the opposite side. The
result is, thus, that here two contact locations are also present
on the joint socket and one contact location on the ring. 6. No
projecting contact region on the ring, three projecting contact
regions on the joint socket. Analogously to the first combination,
as to which pair of the three contact regions of the joint socket
firstly meets a contact location on the ring inner surface is down
to chance. The situation according to the preceding combination
then results with this pair, thus two contact locations on the
joint socket and one contact location on the ring.
With all combinations, in each case a further variant exists, in
that the three contact regions or contact locations which
accommodate the clamping force do not lie on a plane through the
center of the ball surface. In this case, the location of the
contact location, which is defined by two opposite, projecting
contact regions, in each case lies in a plane that leads through
the respective angle bisector and runs normally to the connection
line of the two projecting contact regions. It can happen that the
joint head slips on one or more of these contact regions or contact
locations, until a fourth contact location results. Even then, it
can result that a fourth contact locations arises given an
increasing clamping of the elements and with a deformation of at
least one of the elements. With a fourth contact location, the
distribution of the contact locations can be such that two contact
locations are present on the ring and two contact locations on the
joint socket; or one contact location is present on the ring and
three contact locations on the joint socket
The contact regions on the ring can be arranged such that the
connection lines of the two contact regions to the middle axis of
the eccentric ring form an angle of less than 180.degree. if one
contact location is present on the ring; and form an angle of less
than 170.degree. and in particular less than 100.degree. if two
contact locations are present on the ring.
The contact regions on the joint socket can be arranged essentially
uniformly on the periphery of a lead-through (opening) for the
fastening element, wherein the lead-through is led through the
holding element and the joint socket.
In one embodiment, the eccentric ring is rotatably arranged on the
fastening element, and the joint head comprises an intermediate
element which can be pressed against the joint socket of the
holding element by way of rotating the eccentric ring and, by way
of this, forms a first contact location and locks the ball joint.
Thereby, the joint head comprises at least two segments that are
arranged lying opposite the intermediate element with respect to
the joint head, wherein each of the at least two segments defines a
contact region and thus establishes a further contact location of
the ball joint. Thus, the ring does not contact the holding
element, but rather only presses against the holding element via
the intermediate element. Thus, again three (or for example four)
contact locations are unambiguously defined.
Conversely, according to an analogous embodiment, the eccentric
ring is rotatably arranged on the holding element and the holding
element includes an intermediate element which, by way of rotating
the eccentric ring, can be pressed against the ball surface of the
fastening element and, by way of this, forms a first contact
location and locks the ball joint. Thereby, the joint socket
includes at least two projecting contact regions, which are
arranged lying opposite the intermediate element with respect to
the center of the joint socket, wherein each of the at least two
projecting contact regions defines or establishes a further contact
location of the ball joint. Thus, the ring does not contact the
fastening element, but rather only presses against the fastening
element via the intermediate element.
In one embodiment, the eccentric ring is rotatably arranged on the
fastening element and a section of the eccentric ring can be
pressed against the joint socket of the holding element by way of
rotating the eccentric ring and, by way of this, forms a first
contact location and locks the ball joint. Thereby, the joint head
comprises at least two segments which are arranged lying opposite
the first contact location with respect to the joint head, wherein
each of the at least two segments defines a contact region and thus
establishes a further contact location of the ball joint. Again
three (or for example four) contact locations are unambiguously
defined in this way.
The ball joint can be realised by way of the joint head as well as
the joint socket--with the exception of the contact
regions--comprising spherical surfaces that match one another. In a
further embodiment of the invention, the joint socket is spherical
only in a part-region, and in a remaining region is designed in a
manner opening towards the clamping element, for example conically.
The part-region thereby lies at the side of the holding element
that lies opposite the clamping element, and the remaining region
lies between the part-region and the clamping element. In a further
embodiment, the joint socket is designed to be completely open
towards the clamping element, preferably conically. A ball joint
connection is also formed with the joint socket in the second and
the third embodiment of the invention on account of the spherical
shape of the joint head, and the projecting contact regions can be
arranged accordingly.
According to a further embodiment, the joint socket is only formed
by three contact regions, and no other points of the joint socket
ever come into contact with the joint head.
In one embodiment, the fastening element is designed in an
essentially rotationally symmetrical manner with respect to a
longitudinal axis of the fastening element, wherein a plane, which
leads through the three defined contact locations, does not contain
this longitudinal axis. If indeed this longitudinal axis were to be
in this plane, which lies normally or approximately normally to the
plane of the holding element, then the distance between individual
ones of the contact locations would be limited by the thickness of
the holding element. In turn, the holding moment would be
relatively low due to the proximity of the contact locations. The
mentioned plane of the contact locations can be as parallel as
possible to the plane of the holding element, in order to achieve
an as high as possible holding moment on locking the ball joint.
This, if the ring is attached on the holding element, is
essentially also the plane of the ring or the ring plane (expressed
more precisely: a plane that lies normally to the rotation axis of
the eccentric ring in the holding element).
In one embodiment, the holding element extends in a plane, and a
plane that leads through the three defined contact locations has an
angle of maximal 45 degrees to the plane of the holding element or
to the ring plane of the eccentric ring.
In one embodiment, the smallest distance between the three defined
contact locations is at least 0.8 times the diameter of the joint
head.
In one embodiment, the holding element or the fastening element
(depending on whether the eccentric ring is arranged on the holding
element or fastening element) includes a lock-in element for the
locking-in (engaging or snap-in) retention of the eccentric ring
with regard to a rotation with respect to the holding element or
fastening element. With this, the eccentric ring can be delivered
and held in an "open" position and does not firstly need to be
brought into this position on application of the fastening element.
The lock-in element can be a prominence on one of the participating
elements, or can be a separate part. The ring, for example, yields
elastically on release of the ring from the locked-in position.
The outer side of the clamping element can include a shoulder
and/or a cone, which corresponds to the shape of an annular groove
in the holding element. The clamping element can include one or
more guides, which are suitable for the engagement of the tool, in
order to carry out a clamping movement. This, for example, is one
or two or more undercut openings for inserting a tool for rotating
the eccentric ring.
One or more joint sockets with corresponding annular grooves are
formed on the surgical holding element.
Basically, the described fastening device can also be applied in
other applications, such as, for example, in engineering, for
mountings and stands and likewise. For example, the fastening
device can be applied in wood construction or generally with the
connection of parts that are to be bonded to one another, by way of
two parts after applying an adhesive being screwed to one another
by way of the fastening device and being pulled against one another
with a bias. The elements of the fastening device can be removed
after the bonding has hardened and is stable.
A tool, for example for fixing, locking and releasing a fastening
device as described above includes:
an inner shank with an inner tool tip,
an outer shank with an outer tool tip,
wherein the inner shank is arranged within the outer shank and is
displaceable with respect to the outer shank along a longitudinal
axis of the two shanks.
In one embodiment, the tool can be disassembled or broken down into
at least two units without the use of any tool, by way of at least
the inner shank and further parts connected thereto, as a first
unit, being able to be separated from the outer shank and further
parts connected thereto, as a second unit, and these being able to
be connected again, without the use of a tool.
In one embodiment, the tool can be disassembled by way of the two
units being separable from one another, by way of first bringing
the two units into a certain position by way of a displacement
along a longitudinal axis of the tool, and the two units then being
able to be pulled from one another after rotation about the
longitudinal axis.
In one embodiment of the tool, one of the tool tips is designed to
hook with an element to be rotated therewith, wherein the shank
corresponding to the tool tip is designed in a flexible and
rotationally stiff manner. The tool cannot slip on applying a
torque if the tool tip is hooked with the element to be rotated.
This is important and advantageous with surgical work. The
disadvantage, however, thereby can be the fact that a tilting of
the longitudinal axis of the tool can exert a moment onto the
element to be rotated. The flexible section of the shank is
envisaged for precisely this reason.
In one embodiment of the tool, it is the outer tool tip that is
formed to hook with an element to be rotated therewith, and thus it
is the outer shank that is designed in a flexible and rotationally
stiff manner in an elastic region. Either the inner shank itself
should also be flexible, or space should be left for the bending of
the outer shank, in the same region along the length of the outer
shank, so that the outer shank can bend. The latter, for example,
can be effected by the inner shank being pulled so far inwards that
this region is completely free, or by way of the inner shank having
a tapering at the location of this elastic region, when the outer
shank is in the operating position.
In one embodiment of the tool, it comprises an asymmetrically
acting torque limiter, in particular for the outer shank
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter of the invention is explained in more detail
hereinafter by way of preferred embodiment examples which are
represented in the accompanying drawings. In each case are shown
schematically in:
FIGS. 1-4 show a fastening device and its individual parts, with
contact regions on the ring;
FIG. 5 shows an alternative embodiment of a clamping ring;
FIGS. 6-11 show a fastening device and its individual parts in an
embodiment with contact regions on the holding element;
FIGS. 12-15 show an embodiment with contact regions on the joint
head;
FIGS. 16-19 show an embodiment with contact regions on the joint
head;
FIGS. 20-24 show a fastening device with a screw ring;
FIGS. 25-27 show drill sleeves for use in the fastening device;
FIG. 28 shows a tool for rotating the ring as well as the fastening
element, with a retracted ring tool;
FIG. 29 shows the tool with a pushed forward (advanced) ring
tool;
FIG. 30 shows the tool, disassembled for cleaning;
FIG. 31 shows an exploded drawing of the tool; and
FIGS. 32-34 show a functioning principle of a torque limiter;
DETAILED DESCRIPTION OF THE INVENTION
Basically, the same parts or equally acting parts are provided with
the same reference numerals in the figures.
FIG. 1 shows a fastening device with a holding element 1, a
fastening element 2 as well as with a clamping element 12. FIG. 2
shows the different elements in a sectioned drawing. The fastening
element 2 with a joint head 3 is applied in a holding element 1,
which includes a receiver for the fastening element 2 with a joint
socket 8. The fastening element 2 includes a receiver 6 for a tool,
as well as a shank 4. The shank 4 leads through a lead-through 20
(opening) of the holding element 1. It is provided, for example,
with a thread 5 and can be screwed into a substrate to be fixed or
stabilised, for example into a bone. The fastening element 2 is
rotatably movable in the holding element 1 by way of the ball joint
established by the joint socket 8 and joint head 3. The holding
element 1, however, is not transitorily movable along the fastening
element 2. The ball joint can be locked or fixed by way of a
clamping element or a ring 12. The ring includes an opening 17 as
well as, lying opposite, a flexurally weak location 17, and these
are provided for a simplified assembly of the ring 12 into a
peripheral annular groove 10 of the holding element 1.
FIG. 3 shows the ring 12 alone in two different views 3a and 3b,
and FIG. 4 shows the ring 12 inserted into the holding element 1. A
widening and a pressing-together or contraction of the ring 12 is
rendered possible by way of the opening 17 on the clamping element
or ring 12. Thus, the clamping element 12 can be pressed together
and inserted into the annular groove 10. The clamping element 12 is
secured from jumping out by way of a shoulder 13 on the ring and by
way of a matching shoulder 11 on the annular groove 10. Instead of
the shoulder or additionally, the ring 12 and the annular groove 10
can also be designed conically in a manner corresponding to one
another. Contact regions 16 are present on the ring inner surface
14, and project inwards with respect to the other regions of the
ring inner surface 14, which are part of a ball inner surface 15
for mounting the joint head 3.
The basic manner of functioning of the locking is described in
detail in the initially mentioned WO 2010/121388 A1. For example,
the annular groove 10 is arranged eccentrically with respect to the
center of the joint head 3 and, as the case may be, also with
respect to a longitudinal axis of the fastening element 2. The
center of a ring inner surface 14 of the clamping element 12
displaces by way of rotating the clamping element 12, and thus
locks the joint head 3 with respect to the joint socket 8 or
releases it.
The following applies to all embodiments: The combination of joint
socket 8 and ring inner surface 14 of the clamping ring 12 forms a
joint shell (socket) with an inner surface or joint inner surface,
which can be a ball inner surface 15, in which the joint head 3 is
mounted. Clearly defined regions, on which a clamping force is
exerted onto the joint head 3 on clamping the ring 12, are present
by way of the ring inner surface 14 and/or the joint socket 8
including projecting contact regions 16. These regions define at
least three points, on which the joint head 3 is held, and thus its
orientation is unambiguously defined.
It is the case for the embodiment of FIGS. 1-4 that the projecting
contact regions 16 first come into contact with the ball surface 9
of the joint head 3 before the other regions of the ring inner
surface 14, and exert a force onto the joint head 3. The joint head
3 is pressed against an oppositely lying point of the joint inner
surface or ball inner surface 15 on the joint socket 8 by way of
this, and this point forms a third point as a further contact
location for fixing the joint head 3. In the case that the joint
head 3 slips at this point (wherein, for example, it is rotated
about a connection line of the two contact regions 16) the joint
head can abut against a fourth point of the ball inner surface 15,
which finally limits the movement of the joint head 3. The
orientation of the joint head 3 and thus of the fastening element 2
is securely defined and is fixed at the contact regions or contact
locations by the clamping force, with this fixation via three or at
the most four points (pronounced contact regions and contact
locations resulting therefrom).
FIG. 5 shows a ring 12 in another embodiment. This comprises an
outer opening 21a, and accordingly, a thinner, flexurally weak
region of the ring (with regard to bending within the plane of the
ring). The outer opening 21a thus projects from the outside in the
direction of the center of the ring into this. This can be a
regular joint inner surface or ball inner surface 15 without
projecting prominences. The ring 12 in the flexurally weak region
is not supported by the flank of the annular grove 10 in the
holding element and deforms outwardly (represented in a dashed
manner in FIG. 5, and for a better overview with a greatly
exaggerated deformation), on clamping the ring 12 between the
holding element 1 and the fastening element 2 (not represented in
FIG. 5). The greatest pressing forces between the joint head 3 and
the inner surface 14 of the ring 12 occur in transition regions
21b, in which the flexurally weak location begins or ends. This
corresponds to two further contact regions 16a, which thus clamp
and hold the joint head 3, together with an oppositely lying
contact location on the holding element 2 that results from this,
at three points. The position of the two contact regions 16a as
well as of the oppositely lying contact location on the holding
element 2 is thus unambiguously defined by the position of the
transition regions 21b on the ring 12.
FIG. 6 shows a fastening device in a further embodiment, FIG. 7 in
a sectioned drawing. The elements with regard to their shape and
function are basically the same, with the difference that no
projecting contact regions 16 are present on the ring 12, but
projecting contact regions 16 are present on the holding element 1
on the joint socket 8 as part of the joint inner surface or ball
inner surface 15, for example in the region of the lead-through 20.
FIG. 8 shows a plan view from the side of the joint socket 8 onto
the holding element 1, with an inserted ring 12, and FIG. 9 the
same view without the ring 12. FIG. 10 shows a view from below,
i.e. from the side of the lead-through 20. FIG. 11 shows a cross
section through a holding element 1 with an inserted ring 12.
A lock-in (detent) element 19 projects into the annular groove 10
and engages into a corresponding recess 22 on the shoulder of the
ring 12 (see FIGS. 3a and 3b). The lock-in element as drawn can be
realised by an inserted pin for design reasons, but according to
other embodiments can also be shaped in a pronounced manner as part
of the annular groove 10 on the holding element 1. Depending on the
design of the recess, the ring can lock in and be held in a defined
position, in which the fastening element 2 can be inserted without
further ado and/or the rotation movement of the ring 12 can be
limited to a predefined region, by way of the cooperation of the
lock-in element 19 and the recess on the ring. Such a lock-in
element 19 can of course be realised also with the embodiments of
FIGS. 1-4.
The opening 17 and/or a further opening 21 of the ring 21 can be
designed in an undercut manner, and then a tool for rotating the
ring 12 can be introduced into the opening 17, 21 and by way of
rotation about the rotation axis of the ring 12 can be hooked with
this ring. This means, for example, that the region, through which
the tool is inserted into the opening 17, 21, is smaller than a
region of the opening 17, 21, which lies further inwards. The tool
thus does not slip out of the opening 17, 21 with a pulling force
along the axis of the fastening element or the tool. The tool is
held back by sections of the ring that project over a part of the
opening 17, 21. The flanks of these sections can be obliquely
shaped, so that the tool is pulled into the opening 17, 21 on
rotating the tool about the axis. This analogously applies to one
or more further sections of the ring 12, for example for a further
opening 21 lying opposite the opening 17, 21, in the region of the
flexurally weak location, as is visible in FIG. 3b. The position of
undercut regions on both sides of the opening 17 is indicated by
way of dotted lines in FIG. 3b. Such an undercut opening 17, 21 can
be realised with the embodiments of FIGS. 1-4 as well as FIGS.
5-10.
It is analogously the case with the embodiment of FIGS. 6-11 that
the projecting contact regions 16 on clamping come into contact
with the ball surface 9 of the joint head 3 before the other
regions of the joint socket 8, and exert a force on the joint head
3. The joint head 3 is pressed against an oppositely lying point of
the joint inner surface or ball inner surface 15 on the ring inner
surface 14 by way of this, the point forming a further contact
location for fixing the joint head 3. The orientation of the joint
head 3 and thus of the fastening element 2 is securely defined way
with this fixation via three or at most four points (projecting
contact regions and contact locations resulting therefrom), and is
fixed by way of the clamping force on the contact regions or
contact locations.
FIGS. 12 to 15 show different views and sections of an embodiment
with contact regions on the joint head, wherein the ring 12 is
rotatably arranged on the joint head 3. The joint inner surface 15
of the joint socket 8 can be a regular spherical inner surface
without projecting prominences. The ring 12 is an eccentric ring
and is rotatably arranged about a middle part 43 of the joint head
3, about an axis which is eccentric, thus is not identical to the
longitudinal axis of the fastening element 2, and does not lead
through the center of the ball joint. The joint head 3 comprises
three segments 42, of which one, hereinafter indicated as
intermediate element 41, can be shaped such that it is elastically
more yielding (pliant) than the other segments with respect to
radial forces. The three segments 42, 41 are arranged distributed
roughly uniformly about the periphery of the joint head 3, outside
the ring 12 in the radial direction. Their shape at their outer
sides corresponds to the ball surface 9 of the joint head 3. On
rotating the ring 12, a section of increasing thickness of the ring
12 can be pushed between the middle part 43 and the intermediate
element 41, by which means the intermediate element 41 is pressed
outwards in the radial direction and against the joint inner
surface 15 of the holding element 1. The joint head 3 is clamped in
and locked between the intermediate element 41 and the other two
segments 42 by way of this. Three projecting contact regions 16
which define the contact locations on the joint are thus defined by
the outer sides of the segments 42 and of the intermediate element
41.
FIGS. 16 and 19 show different views and sections of another
embodiment with contact regions on the joint head, wherein the ring
12 is rotatably arranged on the joint head 3. The joint inner
surface 15 of the joint socket 8 can be a regular spherical inner
surface without projecting prominences. The ring 12 is an eccentric
ring and is rotatable about a middle part 43 of the joint head 3,
about an axis which is eccentric, thus not identical to the
longitudinal axis of the fastening element 2 and does not lead
through the center of the ball joint. The joint head 3 includes two
relatively short segments 42. The two segments 42 are arranged at
two of three locations, which are distributed roughly uniformly
about the periphery of the joint heed 3, outside the ring 12 in the
radial direction. At their outer sides, the shape of the segments
42 corresponds to the ball surface 9 of the joint head 3. A contact
location can be formed on the third of the mentioned three
locations, between the ring 12 and the joint inner surface 15 of
the joint socket 8. For this, a section of a greater thickness of
the eccentric ring 12 can be pressed against the joint inner
surface 15 by way of rotation of the ring 12. The joint head 3 is
clamped and locked between this contact location and the other two
segments 42 by way of this. Two projecting contact regions 16 are
thus formed by the outer sides of the two segments 42. They define
three contact locations on the joint: these on the one hand are the
two contact regions 16 and on the other hand the location on the
ring 12, the location lying opposite the two contact regions 16 or
segments 42.
The shortened segments 42 of the embodiment of FIGS. 16-19 can also
be used in the embodiment of FIGS. 12-15, and conversely, the
larger segments 42 of the embodiment of FIGS. 12-15 in the
embodiment of FIGS. 16-19. With the embodiments of FIGS. 12-19, the
joint socket 8 can comprise projecting contact regions 16 as with
the embodiment of FIGS. 6-11.
FIGS. 20-24 show a fastening device, in which a screw ring 12a is
rotatably arranged on the joint head 3. The screw ring can be
rotatable about an axis through the center of the ball joint, thus
in a non-eccentric manner with respect to the joint head 3. The
joint head 3 in the peripheral direction comprises several segments
42 which are separated from one another by slots and by way of this
can be pressed outwards. An inner side of the segments 42 (seen in
the radial direction) is conically shaped, and the screw ring is
shaped as a corresponding outer cone on its outer periphery. The
segments 42 are pressed outwards and against the joint socket 8 by
way of screwing the screw ring 12a onto the middle part 43, by
which means the joint is locked.
Sections of a surgical holding instrument 1 are shown in each case
in FIGS. 1-24. A complete surgical holding element 1 preferably
includes several receivers for fastening elements 2. Embodiments
with only one joint could be applied with applications on the
vertebral column.
FIGS. 25 and 26 show drill sleeves 30 for use in the fastening
device, in a front view and in section. A drill sleeve 30 includes
a cylindrical guide opening 31 for guiding a drill. An inner
diameter of the guide opening thus corresponds to an outer diameter
of the intended drill. The drill sleeves 30 are shaped the same as
the joint heads, with an outer ball surface 34, at the outer side,
and thus, with the joint socket 8 and the ring 12, form a ball
joint. Thus, this ball joint can also be locked by rotating the
ring 12. Several drill sleeves 30 can be connected to one another
with connection elements or connection ribs 32. These connection
ribs 32 form a loss prevention and permit a simple handling of a
set of drill sleeves 30. The connection ribs 32 can be formed of an
elastic material and can include compensation regions 33, so that
the drill sleeves 30, per se, can be moved, in particular for
setting their orientation in the joint sockets 8. The drill sleeves
30, for example, are manufactured from a resorbable material that
can be broken down in the body, so that swarf or wear arising on
drilling is of no problem. FIG. 27 shows a drill sleeve 30 with an
abutment 35, which limits the rotation of the drill sleeve 30 in
the joint socket 30. The abutment 35 can be a projecting ring or
several projecting elements, which are arranged in a ring-like
manner and which are arranged in a plane normal to the axis
direction of the guide opening. They limit a rotation of the drill
sleeve to a maximal angle deviation from a normal to the surface of
the holding element 1 by way of this.
The drill sleeves 30 are used for guiding a drill for the
pre-drilling of holes, typically in a bone, before the insertion or
screwing-in of the fastening elements or screws 2. For this, the
drill sleeves 30 can be applied into the holding element 1 before
use or can be delivered already in an inserted manner. The drill
sleeves 30 can be orientated according to requirement already
before the insertion of the holding element 1, and then be locked
by way of the ring 12. The holding element 1 is then brought into
the desired end position with respect to the bone to be held, and
the bores are created in the bone with the help of the drill
sleeves 30. The respective drill sleeve 30 can thus be removed if
the respective fastening element 2 is to be inserted after the
drilling of a hole, before the other holes are drilled. Thereby,
the connection ribs 32 to other, still inserted drill sleeves are
cut through or severed or are broken away for example at a breakage
location (not shown).
A tool as is represented in the FIGS. 28 to 31 in different
sections and views can be used for work with the fastening device,
i.e. for rotating and in particular for screwing the fastening
element 2 and for rotating and thus locking or unlocking the ring
12. The tool as two main constituents comprises: an inner shank 103
with an inner tool tip 117. This, for example, is shaped
corresponding to the receiver 6 of the fastening element 2. The
inner tool tip 117 can thus be shaped according to common types of
screwdrivers, such as a slot screwdriver, cross-head screwdriver,
Philips screwdriver, Pozidriv, hexagonal or Torx screwdrivers. The
inner shank 103 is assembled on a grip 109. an outer shank 114 with
an outer tool tip 116, which can be shaped in a manner
corresponding to the opening or openings 17, 21 of the ring 12, for
example in an undercut manner, so that the outer tool tip 116 hooks
in the opening or openings 17, 21, by which means a slipping of the
tool is prevented and a secure force transmission or torque
transmission on the ring is possible. The outer shank 114 is
assembled on a telescopic sleeve 107.
The outer shank 114 and the telescopic sleeve 107 are displaceable
with one another with respect to the inner shank 103 and the grip
109, along a longitudinal axis, thus in the axial direction. The
inner shank 103 thereby runs within the outer shank 114, for
example in a coaxial manner. The outer shank 114 in a first
displacement position (FIG. 28) is retracted, so that the inner
tool tip 117 can be used. The outer shank 114 is extended or pulled
out in the second displacement position (FIG. 29), so that the
outer tool tip 116 can be used.
A locking element 106 is provided for locking in the two
displacement positions and a release element 105 which can be
actuated by way of a release button 101 (FIG. 31) can be actuated
for lifting the locking. The locking element 106 includes a locking
head 106a, as well as elastic locking tongues 106b with locking
detents 106c at their end. The locking detents 106c lock in from
the inside on the rear or front detent grooves 118, 119 of the
telescopic sleeve 107. In the first displacement position (FIG. 28)
they lock in the front detent groove 118, and in the second
displacement position (FIG. 29) in the rear detent groove 118. For
releasing the locking, the release button 101 is pushed inwards
against the force of a spring 102, by which means the release
element 105 in each case with a release finger 105a pushes or
slides over the locking tongues 106b and presses the locking
tongues 106b inwards, and with this also presses the locking
detents 106c inwards and pulls them out of the detent groove.
If this release is effected in the first displacement position
(FIG. 28), thus with a retracted outer shank 114, then the
telescopic sleeve 107 together with the outer shank 114 is pushed
forwards by a spring 110. A brake is provided, so that in the case
of an inadvertent actuation of the release button 101 during the
work with the inner tool tip 117, the outer tool tip 116 abuts
against the plate or the ring, and this brake limits this movement.
For this, the inner side of the telescopic sleeve 107, which moves
along the locking tongues 106b and the locking detents 106c can
comprise a narrowed location or brake location 108 that along the
movement direction of the locking tongues 106b is located in front
of the rear detent groove 118. If the telescopic sleeve 107 moves
to the front, the locking tongues 106b at the braking location 108
abut against the inner side of the telescopic sleeve 107, are
pushed inwards and thereby brake the movement of the telescopic
sleeve 107, before the outer tool tip 116 gets into the region of
the inner tool tip 117. The telescopic sleeve 107 is pushed to the
front by hand, until the locking tongues 106b lock in the rear
detent groove 118 (FIG. 29), in order to bring the outer shank 114
into the frontmost, completely extend displacement position.
A torque is to be transmitted from the hand grip 109 onto the
respectively active tool tip 116, 117 when working with the
tool.
If the inner tool tip 117 is active, then the torque is led via the
following parts: hand grip 109-screws or pins 123 (not visible in
FIGS. 28 and 29)-locking head 106a-pin 104-inner shank 103-inner
tool tip 117.
If the outer tool tip 116 is active, the torque is led further
departing from the inner shank 103, via the following parts: inner
shank 103-slot 120 of the inner shank-pin 111 of the telescopic
sleeve 107-telescopic sleeve 107-torque limiter 112-outer shank
114-outer tool tip 116.
The mentioned slot 120 of the inner shank runs in the longitudinal
direction of the inner shank 103 such that the pin 111 of the
telescopic sleeve 107 projects into the slot 120 irrespective of
the displacement position.
The mentioned torque limiter 112 is arranged between the front end
of the telescopic sleeve 107 and an end-piece 114a of the outer
shank 114. The end-piece 114a is pulled with a sleeve head 113,
which is fastened on the telescopic sleeve 107, against the torque
limiter 112. Thereby, a sliding element 124 for reducing the
friction can be arranged between the sleeve head 113 and the
end-piece 114a.
The tool can be disassembled without any tools, in order to meet
hygiene regulations for medically used instruments (FIG. 30). With
this, on the one hand the release element 105 with the release head
101 and, on the other hand, the telescopic sleeve 107 with the
outer shank 114 can be separated.
In order to separate the telescopic sleeve 107, the slot 120 of the
inner shank comprises two sections, in which the pin 111 can slide:
a first section 120a for the torque transmission, with a length
corresponding to the two displacement positions, and a second
section 120b for the disassembly of the telescopic sleeve 107. The
two sections 120a, 120b run parallel to one another, offset to one
another in the peripheral direction of the inner shank 103. The
first section 120a is limited in its length and by way of this
limits the movement of the telescopic sleeve 107 along the inner
shank 103. The first section 120b, however, leads further to the
tip of the inner shank 103 and is open towards the tip. The second
section 120b runs into the first one at a transition location 120c.
Thus, for disassembly, the telescopic sleeve 107 by way of
displacement in the axial direction can be brought into a
displacement position, in which the pin 111 lies at the transition
location 120c. The telescopic sleeve 107 can then be rotated about
the axial direction, by which means the pin 111 gets into the
second section and the telescopic sleeve 107 can be pulled off from
the inner shank 103. According to one embodiment, moreover the slot
120 at the transition location 120c is not as deep as in the first
section 120a, and the pin 111 is pressed into the slot 120 by a
spring. Then, on rotation of the telescope sleeve 107, an
additional force must be applied, in order to push the pin 111
outwards. This results in a security against inadvertent
disassembly.
In order to separate the release element 105, a slot 121 is present
in the release fingers, in which slot, for example, the pin 104
projects in the radial direction. On pressing the release element
105, the slot 121 moves along the pin 104, wherein the movement of
the release element 105 in the longitudinal direction of the tool
is limited by the length of the slot 121. The slot 121 includes a
lateral opening, so that the release element 105 is rotatable about
the longitudinal axis of the tool when this opening is located at
the height of the pin 104, whereupon the release element 105 can be
pulled out.
In the previous description, in each case there was mentioned only
one slot 120 of the inner shank and one pin 111 running therein. It
is to be understood that two, three or more slots 120 and
corresponding pins 111 can be arranged or distributed about the
periphery of the tool, for an improved force transmission.
Due to the fact that according to one embodiment, the outer tool
tip 116 can hook, for example, with a ring 12 of a fastening
element 2, and due to the lever arm that the tool forms, large
forces can occur on the fastening element 2. This can lead to
damage and/or to the displacement of the fastening element or of
broken bones connected thereto. So as to prevent this, the outer
shank 114 can be designed in a flexible and rotationally stiff
manner or include an elastic region 115 that has an increased
elasticity, in particular bending elasticity compared to the other
regions of the outer shank 114, but is rotationally stiff, in order
to be able to transmit a torque. For example, spiral-like incisions
or recesses can be present on the outer shank 114 in a manner of a
helical coupling, or a helical spring can be installed. The inner
shank 103 is designed in a tapered manner at the height of the
elastic region 115 (with a pulled-out outer shank) and further to
the front, towards the inner tool tip 117, so that the inner shank
103 does not block the bending of the outer shank 114.
The torque limiter 112 can comprise two resilient elements pressed
against one another, which produce a torque due to friction. The
FIGS. 32 to 33 alternatively show the manner of functioning of one
variant for an asymmetrically acting torque limiter 112. What is
shown in each case is a section of an upper ring 112a and of a
lower ring 112b which are pressed against one another by way of a
force F in the axial direction, thus parallel to the longitudinal
direction of the tool. The two rings 112a, 112b comprise
projections 112c which are shaped symmetrically to one another.
Several such projections 112c are distributed regularly in the
peripheral direction about the rings 112a, 112b. Balls or rollers
11d are arranged between the two rings. If the rings 112a, 112b
rotate against one another about the axial direction, then they
roll on one another via the rollers 112d, until the rollers 112d
abut on the projections 112c. Depending on a steepness of the
flanks of the projections, a multiple or a fraction of the force F
is to be applied on each projection in the horizontal direction, in
order to distance the rings 112a, 112b to one another. A
corresponding maximal torque, at which the torque limiter slips,
results from this. The maximal torque in the two rotation
directions can be separately selected by way of the different
steepness of the flanks at the two sides of the projections 112c.
With the shown example in FIG. 32, the lifting of the upper ring
112a and, thus, the slipping begins with a first torque. In the
position according to FIG. 33, the counter-moment produced by the
limiter already reduces again according to the course of the
profile of the projections 112c. With a rotation movement in the
opposite direction, the maximal moment required for slippage in the
counter direction is significantly higher according to the steeper
flank on the opposed side (FIG. 34).
For the described tool, the maximal moment on locking the fastening
device (for example by way of rotation in the clockwise direction)
is determined by the design and the materials of the fastening
device. In contrast, a higher maximal moment is set for
unlocking.
* * * * *